Errant laser beam safety sensors are required on most high power lasers (e.g., the airborne laser (ABL) and the Advanced Tactical Laser (ATL) Advanced Component Technology Demonstration (ACTD)) to mitigate catastrophic events. Errant beam failures can be caused by pointing errors from actuated or drifted optics, or by failure of reflective optical coatings, or by substrate fracture, which allows the errant beam to travel through the optical substrate. Optical coating failure can cause extensive absorption by the optical substrate causing substrate failure, or the light can transmit through and out the back of the substrate causing serious safety issues. Failure conditions on optical coatings and optical substrates are particularly difficult to detect because coatings can fail in small subapertures (i.e., an area less than the aperture area of the optic in question).
Currently, high energy laser (HEL) abort systems are included in a laser design to quickly deactivate lasing, usually through the use of a high speed shutter that closes once failure conditions are sensed. Previously, detection systems have included optical scattering sensors and burn wires but such detection systems have been expensive to calibrate and implement, and have lacked the capability to effectively detect subaperture coating failures.
Accordingly, a system and method for accurately and effectively detecting errant laser beams are highly desirable, especially errant beams caused by subaperture optical coating failure.